1. Field of the Invention
The present invention relates to an electronic or electric device such as a personal computer, a computer game machine or a printer, which has a cooling fan housed in a case. The present invention also relates such a cooling fan and a case used for the electric device.
2. Description of the Prior Art
An electronic or an electric device such as a personal computer, a computer game machine or a printer includes various electromechanical parts housed in a case. Since the inside of the case becomes high temperature due to heat generated by a CPU and/or IC chips, or electromechanical parts, a cooling fan is disposed in the case. This fan is usually arranged at a vicinity of an opening (an exhaust hole) formed in the side-wall of the case. The inside air of the case is exhausted through this opening externally, so that the inside of the case is cooled.
This opening is usually provided with a mesh guard that is called a finger guard for preventing a finger or other matters from entering and stopping the fan or from being injured. There are two types of this finger guard as shown in FIGS. 13A and 13B. The first type of the finger guard as shown in FIG. 13A has a shape that is a combination of circular ribs and radial ribs. This type of the finger guard is disclosed in Japanese unexamined patent publication No. 2000-257597 for example. The second type of the finger guard as shown in FIG. 13B has a grid shape formed by plural ribs. This type of the finger guard is disclosed in Japanese unexamined patent publication No. 5-274062 or No. 11-354964.
However, the mesh finger guard attached to the opening as an exhaust hole for the cooling fan may disturb smooth exhausting of air inside the case since the exhaust air may be interrupted by the finger guard. There is another problem that large noise may be generated when the exhaust air is interrupted by the finger guard.
As a measure of this problem, there is a well-known finger guard, in which each of the ribs constituting the cross-section shape of each rib has a round corner portion so that the air resistance caused by the ribs is reduced. However, this measure is not still a sufficient for achieving substantial improvement against the above-mentioned problem.
In these years, higher cooling performance and quieter property are required for an electronic or electric device that has been becoming more powerful and more compact. However, available finger guards up to now cannot satisfy such demands sufficiently.